Electron beam line scanner with zig zag control electrodes

ABSTRACT

A pair of control plate members are utilized to control an electron beam between a cathode and a target in response to binary control signals. Each control plate member comprises a plate of a non-conductive substrate having a resistive coating thereon which is preferably electron secondary emissive. A plurality of electrode elements are arranged in parallel rows on the control plate members between the cathode and target. The electrode elements are formed by conductive strips arranged over the resistive coatings in a binary coded zig-zag pattern. The plate members are positioned with corresponding zig-zag electrode elements opposite each other and in 180* phasal relationship. The zig-zag electrode elements are excited with binary control signals which provide a transverse potential which permits the electron beam to pass from the cathode to only a single selected portion of the target at a time.

1 I United States Patent 1151 3,683,230 Blinghamet al. 1 Aug. 8, 1972 [54] ELECTRON BEAM LINE SCANNER 3,108,203 10/1963 Crowell ..315/8.5 WITH ZIG ZAG CONTROL 3,408,532 10/1968 Hultberg et al ..3l5/I2 ELECTRQDES 3,483,422 l2/l969 Novotny ..315/l2 [72], Inventors: Ronald H. Bingham, Torrance; Ed- Primary Examiner Reuben Epstein Guava", lnglewwd, Attorney-Sokolski & Wohlgemuth and w. M. of Calif. Graham [73] Assignee: Northrop Corporation, Beverly Hills, Calif. ABSTRACT [221/ Filed. May 22, 1970 A pair of control plate members are utilized to control an electron beam between a cathode and a target in PP 39,898 response to binary control signals. Each control plate member comprises a plate of a non-conductive sub- Related Application Data strate having a resistive coating thereon which is [63] Continuation-impart of Ser. No. 755,276, Au preferably electron secondary emissive. A plurality of 1 26, 1968, ab nd ned, electrode elements are arranged in parallel rows on the control plate members between the cathode and 521 11.5. 111 .315/12, 313/68, 313/78, target The electrode elements are formed y conduc- 3 5 5 3 2 9 32 2 tive strips arranged over the resistive coatings in a bi- 51 Int. Cl ..H01j 29/74, H0lj 31/06, 1101 29/41 nary coded e- P The Plate members are 581 Field of Search .........315/12, 8.5; 328/229, 231; Positioned with corresponding zig-lag elewode 313/105 78 68 8O ments opposite each other and in 180 phasal relationship. The zig-zag electrode elements are excited with [56] References Cited binary control signals which provide a transverse potential which permits the electron beam to pass UNITED STATES PATENTS from the cathode to only a single selected portion of the target at a time. 2,916,662 12/1959 Van Overbeek et al.....3l5/l2 3,088,047 4/1963 Groendijk et al ..315/8.5 14 Claims, 6 Drawing Figures J 45 4 42 4 9 4/ I 43 CLOCK g ADDRESSING COUNTER CONTROL 264 26 26C 26a. 2491 Zeb 32/2 TARGET 32d /4 CATHODE lS-||||| M111 4 P'A'TENIEDN: 8 I972 3,683,230

SHEET 1 BF 2 Q [Z V 520V) '1' 200V.

CHANNEL f TOP PLATE CHANNEL 2 j TIE- n l T CHANNEL L L BOTTOM PLATE CHANNEL 2 b |oo-v (2ov.) +2oov.

"FIE- ;I. I2;-

CHANNEL 2 TOP CHANNEL l I20 TOP 8 BOTTOM CHANNEL 2 BOTTOM POINTS BETWEEN STRIPS TIE-:3. .1:

lA/l/f/VTOBS. FZQNALD H. BINGHAM EDMOND 3. CANAVAN ELECTRON BEAM LINE SCANNER WITH ZIG ZAG CONTROL ELECTRODES This is a continuation in part of our application Ser. No. 755,276, filed Aug. 26, 1968, now abandoned.

This invention relates to electron beam line scanners and more particularly to such a scanner suitable for use a display or memory devices which operates in response to a sequence of binary control signals.

Electron beam scanners utilizing cathode ray tubes for video display and memory storage functions are widely used inthe prior art in such apparatus as display devices and computers. In US. Pat. application Ser. No. 51 1,747, now U.S. Pat. No. 3,408,532 filed Dec. 6, 1965, dated Oct. 29, 1968 and assigned to Northrop Corporation, the Assignee of this application, an electron beam scanning device is described which has distinct advantages over a cathode ray tube in that it is capable of random addressing and has much more compact proportions. Thisdevice utilizes a plurality of coded dynode members located between an electron emitting cathode and a target plate, the dynode members. controlling the electron beam in response to a digital address signal. While, as just noted, the device of this prior application provides distinct advantages over the; cathode ray tube, it requires a voltage differential between adjacent portions of each dynode which is relatively high, i.e., of the order of 200 volts. This voltage differential imposes a voltage breakdown problem in the closely spaced structure. To avoid this problem requires special precautions in manufacture. To overcome .this voltage breakdown problem, an electron beam scanner has. been developed by Northrop Corporation utilizing a relatively small transverse switching potential which is applied between oppositely positioned dynode sections. This particular device utilizes electron beam channels which are coated with either an electron secondary emitting material or an electron absorbing material in accordance with a predetermined binary code pattern.

The device of the present invention provides a transverse switching technique which is an improvement over the aforementioned transverse switching in which the use of electron absorbing areas in combination with electron emitting areas is obviated and the transverse switching to obtainthe desired beam control rather is implemented by electrode elements formed by conductive strips arranged in a predetermined coded zig-zag pattern.

The invention will now be described in connection with the drawings of which:

FIGS. lA-IC are schematic drawings illustrating the operation of the device of the invention,

FIG. 2 is a perspective view illustrating one embodiment of the device of the invention,

FIG. 3 is an exploded perspective bodirnent shown in FIG. 2, and

FIG. 4 is a schematic drawing illustrating control circuitry which may be utilized with the embodiment of FIGS.12 and 3.

Briefly described, the device of the invention comprisesiz a pair of control plate members which are formed on non-conductive substrates, such as glass plates. One of the broad surfaces of each of the substrate plates is coated with a resistive material which may also be secondary emissive, and has a plurality of parallel rows. of conductive strips. The conductive view of the emstrips are arranged in a binary coded zig-zag pattern to form separate electrode control elements. The two control plate members are positioned with corresponding zig-zag electrode elements of each opposite each other and separated by a small spacing defining a linear scanning slot, the zigzag patterns of the electrode elements of one control plate member being out of phase with the pattern of the electrode elements of the other control plate member. A cathode member and a target member are arranged at opposite ends of the control plate members to establish an electron beam thereacross. Binary switching control circuitry is utilized to selectively provide transverse potentials between the oppositely positioned electrode elements in a predesired manner so as to block the passage of electrons between the cathode and the target at all but one selected control plate portion at a time. Each of such control plate portions thus defines an electron beam channel with the excitation of any one of such channels being implemented by the binary control signal.

Referring now to FIGS. 2-4 of the drawings, one embodiment of the device of the invention is illustrated. The device comprises a pair of control plate members 11 and 12 which are positioned with their broad surfaces opposite each other, and with a cathode member 13 along one edge thereof and an anode member 14 along an opposite edge thereof. Control plate members 1 1 and 12 are kept spaced from each other a distance, which in an operative embodiment is of the order of 0.015 inches, by means of spacer members 17 and 18 which may comprise glass plates attached to the ends of members 11 and 12 respectively. The entire assembly is contained within a vacuum tight casing 20 which has been evacuated to provide an adequate vacuum for efficient transmission of the electron beam. Cathode member 13 is preferably of a cold cathode type and may comprise a plate of insulating material such as glass, the surface of which is coated with a radioactive or photo-emissive material. If so desired, a thermionic cathode could also be utilized. Target member 14 may comprise a glass plate coated with phosphorescent material in the case of a display device, or could comprise a memory plate if the scanner is to function as a memory device.

Control plate members 11 and 12, except for the inverse relationship of the zig-zag patterns of their electrode elements, as to be hereinafter pointed out, are identical in construction and each comprises a sub strate 22 of a dielectric material such as glass which has a resistive coating which is preferably also electron secondary emissive, such as lead oxide or tin oxide, on one of the broad surfaces 23 thereof. The resistive coating covers the entire surfaces 23 except for separation areas 230 which effectively insulate the secondary emissive portions forming the electron beam channels (in conjunction with the electrode elements) from each other. Lying over the secondary emissive coatings are a plurality of parallel rows of transversely running electrically conductive narrow strips 25 arranged in a zigzag pattern. Strips 25 may be formed on the substrate plates 22 along with their associated connection terrninals 26a-f by photoresist or etched circuit techniques well known in the art.

versely related or 180 out of phase with the oppositely positioned corresponding strips of control plate member 11.

Between each of zig-zag strips 25 and at the edges of the control plate members are conductive straight line strips which connect to associated terminals 32a-32. Strips 30 and their terminals 32a-32h may be placed on the control plate members in the same manner as strips 25, i.e., by photo-resist techniques.

Thus, each of the control plate members 11 and 12 comprises a resistive surface which is preferably also electron secondary emissive which is traversed by a plurality of conductive strips arranged in a zig-zag binary coded pattern with the zigzag strips of one member being in inverse relationship to that of the other.

It is again to be noted that while it is preferred to V have a secondary emissive surface on plate members 1 1 and 12, the device could be made to operate with surface coatings of resistive material which have little or no secondary emissive properties.

It is further to be noted that the device of the invention could be utilized to control the flow not only of electrons but also other charged particles, such as positive or negative ions.

Referring now to FIG. 4, an accelerating potential for accelerating the flow of electrons between cathode 13 and target 14 is provided by means of direct current power source 35. A potential gradient is provided at intermediate points along the control plate members by means of voltage divider 37 which provides such intermediate potentials to terminal pairs 32b-32f and 32g-32. Connections are made between power source 35 and cathode 13 and target 14 from terminal 32a and 32d. Suitable accelerating voltages are applied by power supplies 53 and 54, respectively.

Connected between each pair of oppositely positioned zig-zag strips 25 is a flipflop switching circuit 41-43, such connections to the zig-zag strips being made through terminals 26a, 26d; 26b, 26e; and 260, 26f, respectively. Each of flip-flops 41-43 has an associated power source 45-47 connected in circuit therewith respectively. Depending upon the state of the associated flipflop, a potential differential is applied between oppositely paired zig-zag strips in one polarity sense or the other. The states of flipflops 41-43 are controlled by clock and counter which operates in response to addressing control circuit 52. Thus, in response to the addressing control, the flipflops 41-43 may be driven to any one of eight combinations of conductive states, i.e., with one or the other of the stages of each flipflops in conduction, each of these eight combinations activating a separate electron beam channel.

Let us now refer to FIGS. lA-lC which schematically illustrate the operation of the control members in achieving the desired control action. A pair of electron beam channels designated as Channel 1 and Channel 2 are shown in FIGS 1a and 1b. Such channels of course are not specifically marked off in an embodiment such as that shown in FIG. 3, but rather are defined by the zig-zag arrangement of the strip elements relative to each other. The locations of such channels are indicated in FIG. 3 by dotted lines 27. A portion of strip elements 25 covering the two adjacent channels designated as Channel 1 and Channel 2 are shown for control members 11 and 12, between a pair of straight line strip members 30a and 30b. As shown, strip members 300 and 3012 have a potential established between them by an external power source (not shown) of 200 volts providing an electron accelerating potential therebetween. In their assembled position, the top plate 12 lies over bottom plate 11 with the corresponding indicated channels superimposed over each other, (i.e., with the portions on each plate marked Channel 1 and those marked Channel 2 opposite each other respectively) and with the zig-zag strip portions 25 in inverse relationship. It is to be noted, thus, that for the convenience of illustration the top plate has been shown in FIG. 1A as looking through the transparent plate from the surface opposite to that on which strip element 25 lies.

A potential difi'erential is established between the strips 25 of plates 11 and 12 in the manner described in connection with FIG. 3. In the illustrative example shown in FIGS. lA-lC, this potential is indicated as volts plus VS (indicated to be 20 volts), and 100 volts minus VS.

FIG. 1C illustrates the voltage gradient established between strips 30a and 30b with the particular potentials indicated in FIGS. '1A and 1B. Thus, a uniform potential gradient is established in the channels between strips 30a and 30b by virtue of the potentials applied between these strips. This potential gradient, however, is modified by the effect of the potentials placed on strips 25. In the case of the portions of strips 25 overlapping Channel 1, the strip portion for control member 11 establishes an 80 volt potential at a point along Channel 1 where an 80 volt potential is already established by virtue of the potential gradient due to the potential between strips 30a and 30b. The portion of strip 25 overlying Channel 1 on top plate 12 similarly establishes a I20 volt potential at the point along Channel 1 where this same potential is established by virtue of the potential between strips 30a and 30b. Thus, as indicated in FIG. 1C, the voltage gradient established on both members 11 and 12 along the Channel 1 portions thereof by virtue of the potential between strips 30a and 30b is not altered by virtue of the potentials applied to strips 25, and thus the gradients for both plates along this channel are the same, and opposite points along the Channel 1 portions of the control members have no significant potential differential therebetween. The electron path between strips 30a and 30b will therefore be relatively undeflected and will either not collide with the surfaces of the control members or will acquire energy between collision as required for the operation of the device.

On the other hand, along the areas indicated as Channel 2 a potential differential is established between the two control plate members as indicated in FIG. 1C, the bottom plate having an 80 volt potential established by virtue of the voltage applied to strip 25, opposite the point on top plate 12 where a volt potential is established by virtue of the voltage gradient. At the same time, a voltage is established at the Channel 2 portion of top plate 12 where strip 25 overlies it of 120 volts, this being opposite a point on bottom plate 11 where only an 80 volt potential exists. Thus, as shown in FIG. 1C, a voltage differential is established all along the oppositely positioned portions of Channel .2 of plate members 11 and 12. This voltage differential causes a deflection of the electron beam transversely between the plates. It has been found that this type of transverse deflection of the electrons causes them to collide with the surface of the plate member so frequently that they do not fall through a sufliciently large longitudinal potential difference betwee'n'collision to produce an actuationsigrialat the targets Operated in this manner the beam is substantially cut off before it reaches the target.

In this manner, the electron beam can be made to pass through any of the desired channels in response to various, combinations of transverse switching potentialsrestablished on zig-zag strips 25. It is to be noted thatby reversing the switching potentials, i.e., by placing 120 volts on the strip element 25 of plate 1 l and 80 volts on the strip element of plate 12, that Channel 2 can be made the active channel and Channel 1 the dormant one.

To furtherillustrate how the embodiment of FIGS. operates, an example of such operation will now be described in connection with these figures. Plus signs have been placed opposite the stages of flipflops 41-43 whichfor the purposes of the example are assumed to establish a positive potential at terminals 26a, 26e, and 26f, with respect to terminals 26d, 26b and 260 respectively Under such conditions, transverse potentials are established in all of the channels to block the passage of an electron beam therethrough except for the first channel wherein electron beam 55 is shown to pass from cathode 13 to target 14. It can clearly be seen that any one of the channels can be activated with a particular combination of flipflop excitation, for example,

Channel 2 .being activated by providing a positive potential at terminals 26a, 26e and 26c with respect to terminals 26d, 26b and 26f respectively, etc.

The; device of this invention thus provides effective means for random electron beam scanning by utilizing a transverse switching potential in connection with zigzag electrode. elements.

We claim:

1.,A charged particle beam line scanner having a source of charged particles, at target, means for accelerating a charged particle beam from said source to saidtarget and means for causing said beam to scan saidtargetin response to a digital addressing signal, said last mentioned means including a pair of :plate members positioned between aid source and target,

said plate members being positioned with one of each of their broad surfaces opposite each other,

means for establishing a similar potential gradient along the broad surfaces of each of said plate members, said gradient running between the source and the target,

conductive strips arranged in a binary coded zig-zag pattern on the. broad surfaces of each of said plate members,

the strip pattern defining a plurality of charged particle beam channels running between the source and target, and

means for selectively applying a potential between corresponding strips of said plate members to provide a transverse potential between said plate members in all but a selected one of said channels at a time.

2. The line scanner of claim 1 wherein the strip pat terns on said plate members are similar but arranged in phase relationship to each other.

3. The line scanner of claim 1 wherein said strips are relatively narrow, encompassing only a small portion of the surface area of saidplate members.

4. The line scanner of claim 1 wherein said means for establishing a potential gradient includes a resistive coating on each of said broad surfaces and power source means connected to said coating.

5. The line scanner of claim 4 wherein said resistive coating is also secondary emissive.

6. An electron beam scanning device comprising:

first and second control plate members, each of said members including a plate substrate of dielectric material,

a secondary emissive coating on one of the broad surfaces of said substrate,

a plurality of conductive strips arranged in a binary coded zig-zag pattern extending in substantially parallel rows across said broad surface, said strips forming control electrode elements,

means for positioning the broad surfaces of said control plate members opposite each other with a spacing therebetween, corresponding electrode elements of said plate members being opposite each other with their zig-zag patterns in a 180 phasal relationship,

a cathode member,

a target member,

said cathode and target members being positioned on opposite edges of said plate members to provide electron beam paths therebetween across said electrode elements,

means for providing an electron accelerating potential between said cathode and said target members, and

means for providing potentials between corresponding pairs of electrode elements of said plate members in predetermined polarities to cause an electron beam to pass from said cathode member to a preselected portion of said target member.

7. The device as recited in claim 6 wherein said spacing between said plate members defines a linear scan slot between said cathode and target.

8. The device as recited in claim 6 wherein said secondary emissive coatings have separation areas for separating the portions thereof corresponding to separate legs of the zigzag patterns of said conductive strips.

9. The device as recited in claim 6 wherein said means for providing an electron accelerating potential between said cathode and target includes straight line conductive strips placed on said plate members between said rows of electrode elements and means for applying potential differentials between successive ones of said straight line strips.

10. An electron beam line scanner having a cathode, a target means for accelerating an electron beam from said cathode to said target and control means for causing said beam to scan said target in response to a random digital addressing signal, said control means including a pair of plate members of a dielectric material, said plate members being positioned with one of each of their broad surfaces opposite each other with a space therebetween, said plate members each having a secondary emissive coating and a plurality of electrode elements on said broad surfaces thereof, said electrode elements comprising conductive strips arranged in a binary coded zig-zag pattern and in substantially parallel rows, the strip pattern defining a plurality of electron beam channels, and means for selectively applying a potential between corresponding electrode elements of said plate members to provide a transverse potential between said plate members in all but a selected one of said channels at a time.

11. The device of claim 10 wherein said means for selectively applying a potential between corresponding electrode elements comprises a separate flipflop circuit connected between each corresponding pair of said elements, said flipflop circuits operating in response to said digital addressing signal.

12. The device of claim 10 wherein the zig-zag pattern of the electrode elements of one of said plate members is positioned opposite corresponding portions of the zig-zag pattern of the other of said plate members in a phasal relationship.

13. The device of claim 10 wherein said space between said plate members is the shape of a narrow linear slot to define a straight line scanning beam.

14. The device of claim 10 wherein said secondary emissive coatings have separation areas formed therein for separating the portions thereof corresponding to separate legs of the zigzag patterns of said strips. 

1. A charged particle beam line scanner having a source of charged particles, a target, means for accelerating a charged particle beam from said source to said target and means for causing said beam to scan said target in response to a digital addressing signal, said last mentioned means including a pair of plate members positioned between aid source and target, said plate members being positioned with one of each of their broad surfaces opposite each other, means for establishing a similar potential gradient along the broad surfaces of each of said plate members, said gradient running between the source and the target, conductive strips arranged in a binary coded zig-zag pattern on the broad surfaces of each of said plate members, the strip pattern defining a plurality of charged particle beam channels running between the source and target, and means for selectively applying a potential between corresponding strips of said plate members to provide a transverse potential between said plate members in all but a selected one of said channels at a time.
 2. The line scanner of claim 1 wherein the strip patterns on said plate members are similar but arranged in 180* phase relationship to each other.
 3. The line scanner of claim 1 wherein said strips are relatively narrow, encompassing only a small portion of the surface area of said plate members.
 4. The line scanner of claim 1 wherein said means for establishing a potential gradient includes a resistive coating on each of said broad surfaces and power source means connected to said coating.
 5. The line scanner of claim 4 wherein said resistive coating is also secondary emissive.
 6. An electron beam scanning device comprising: first and second control plate members, each of said members including a plate substrate of dielectric material, a secondary emissive coating on one of the broad surfaces of said substrate, a plurality of conductive strips arranged in a binary coded zig-zag pattern extending in substantially parallel rows across said broad surface, said strips forming control electrode elements, means for positioning the broad surfaces of said control plate members opposite each other with a spacing therebetween, corresponding electrode elements of said plate members being opposite each other with their zig-zag patterns in a 180* phasal relationship, a cathode member, a target member, said cathode and target members being positioned on opposite edges of said plate members to provide electron beam paths therebetween across said electrode elements, means for providing an electron accelerating potential between said cathode and said target members, and means for providing potentials between corresponding pairs of electrode elements of said plate members in predetermined polarities to cause an electron beam to pass from said cathode member to a preselected portion of said target member.
 7. The device as recited in claim 6 wherein said spacing between said plate members defines a linear scan slot between said cathode and target.
 8. The device as recited in claim 6 wherein said secondary emissive coatings have separation areas for separating the portions thereof corresponding to separate legs of the zig-zag patterns of said conductive strips.
 9. The device as recited in claim 6 wherein said means for providing an electron accelerating potential between said cathode and target includes straight line conductive strips placed on said plate members between said rows of electrode elements and means for applying potential differentials between successive ones of said straight line strips.
 10. An electron beam line scanner having a cathode, a target means for accelerating an electron beam from said cathode to said target and control means for causing said beam to scan said target in response to a random digital addressing signal, said control means including a pair of plate members of a dielectric material, said plate members being positioned with one of each of their broad surfaces opposite each other with a space therebetween, said plate members each having a secondary emissive coating and a plurality of electrode elements on said broad surfaces thereof, said electrode elements comprising conductive strips arranged in a binary coded zig-zag pattern and in substantially parallel rows, the strip pattern defining a plurality of electron beam channels, and means for selectively applying a potential between corresponding electrode elements of said plate members to provide a transverse potential between said plate members in all but a selected one of said channels at a time.
 11. The device of claim 10 wherein said means for selectively applying a potential between corresponding electrode elements comprises a separate flipflop circuit connected between each corresponding pair of said elements, said flipflop circuits operating in response to said digital addressing signal.
 12. The device of claim 10 wherein the zig-zag pattern of the electrode elements of one of said plate members is positioned opposite corresponding portions of the zig-zag pattern of the other of said plate members in a 180* phasal relationship.
 13. The device of claim 10 wherein said space between said plate members is the shape of a narrow linear slot to define a straight line scanning beam.
 14. The device of claim 10 wherein said secondary emissive coatings have separation areas formed therein for separating the portions thereof corresponding to separate legs of the zig-zag patterns of said strips. 